May 20 (Reuters) - A group of former National Football League players filed a class-action lawsuit on Tuesday, claiming the league illegally drugged players with pain medicine and encouraged them to play injured in order to keep league profits flowing for more than 30 years.

The suit, filed in U.S. District Court in the Northern District of California, lists eight former players as defendants and claims more than 500 other "retained" plaintiffs who played between 1969 and 2008.

The suit alleges that player Keith Van Horne, who is a plaintiff in the lawsuit, played an entire season with a broken leg without knowing his leg was broken. Van Horne, an offensive tackler for the Chicago Bears from 1981 to 1993, was given a medical boot to wear and fed a "constant diet of pills to deal with the pain," the suit alleges.

The NFL has sanctioned and encouraged the misuse of narcotics and other medications, sometimes in combination with alcohol despite known risks, the lawsuit claims.

The lawsuit seeks unspecified compensatory and punitive damages and seeks an injunction to provide for medical monitoring.